The invention relates generally to the field of apparatus having environmentally controllable chambers, such as devices for stressing or testing electronic circuit components. More particularly, the present invention relates to a device for seating printed circuit boards into such apparatus, and still more particularly, to a device for automated seating and unseating of burn-in boards carrying circuit components within a burn-in chamber.
Integrated (IC) circuit packages and other semiconductor products are mass-produced and installed in electronic circuits within highly sophisticated, complex and costly equipment. As with many mass-produced products, IC packages are prone to failure, in some cases within the first one thousand hours of operation. The complexity of equipment within which such packages are installed makes post-installation failures highly undesirable. For example, when equipment reaches the final inspection stage of production, before failures are detected, the high level skills required for inspection and repair add a significant cost to production expenses. Even more significantly, when the product has been installed in the field and a service technician must make warranty repairs, the costs thereby incurred can have a significant effect on profitability. More and more often, however, post-installation failures simply cannot be tolerated because of the potentially disastrous consequences. As a result, manufacturers of electronic equipment are demanding ever greater quality and dependability in commercial grade IC packages.
Quality and dependability are enhanced substantially by early detection of those IC packages likely to fail early, prior to the installation of the IC packages in equipment. One method for detecting flawed IC packages is referred to as "burn in." "Burn-in" generally involves a technique for stressing and possibly also testing IC packages within their physical and electrical limits to discover IC packages that may be prone to early failure, or to enable the grading and sorting of IC packages according to performance specifications. One burn-in technique includes loading a large number of IC packages into sockets on numerous printed circuit, or burn-in boards; placing the burn-in boards into a housing with a chamber having an environment, particularly temperature, that is closely controllable; applying electrical test signals to each IC package on each burn-in board while uniformly subjecting the IC packages to the same temperature for a specific period of time; removing the boards from the chamber; and unloading the IC packages from the burn-in boards for sorting, distribution, and use or disposal.
Prior art burn-in chambers are shown, for example, in U.S. Pat. No. 5,359,285 to Hashinaga et al., and U.S. Pat. No. 5,003,156 to Kilpatrick et al. Typical prior art burn-in chambers have a front opening that allows access to the chamber and to racks for holding burn-in boards. An example of a "burn-in" chamber of the prior art holds up to seventy-two burn-in boards on racks disposed in the chamber, each board holding hundreds of IC packages. The chambers also typically include electrical connections in the rear of the chamber aligned with the racks for electrical source connection with the IC packages on the boards. For each burn-in board, there may be between 15 and 20 "spring clip" type electrical connections that must be engaged for burning-in the boards.
Various deficiencies and problems have been encountered with prior art techniques and devices used for seating and unseating burn-in boards in burn-in chambers. As used herein, the terms to "seat" and "seating" a burn-in board means moving the board that has already been placed in the chamber, such as on a burn-in board rack, into connection with the electrical ports in the rear of the chamber. Most prior art techniques are slow and not cost efficient. Typical techniques involve manually seating the boards, or using devices, such as, for example, crowbar type devices, that are cumbersome and can cause damage to the burn-in boards or chambers.
For example, seating a single burn-in board within corresponding electrical spring clip connectors typically requires a significant force, such as, in some cases, up to 90 pounds of force. As a result, manual seating of burn-in boards is difficult and time consuming. If the boards are seated with too great force, or are seated or unseated with improper alignment of the burn-in boards and electrical connections in the chamber, such as with the use of crowbar-like devices, the boards and connections are subject to damage and malfunctioning. Furthermore, unseating typically requires gripping the burn-in board and drawing, or pulling, the board outwardly, disconnecting the board from the electrical connections. Because the frames and faces of burn-in boards typically have sharp protrusions and edges, manual seating and unseating boards is dangerous and difficult. Similar problems exist with other types of chambered devices used for stressing and testing electronic circuit components and other types of devices having environmentally controllable chambers used with printed circuit boards.
Thus, there remains a need for a device and method for seating printed circuit boards, such as burn-in boards, in chambers that is quicker and more cost effective than previous devices and methods. Preferably, the seating device will be easy to operate, move between various positions and be capable of seating boards located at different heights within the chamber. Especially well received would be a seating device that can be automatically controlled and requires minimal operator assistance; and a seating device that requires minimal space around the chamber, such as a seating device that can be connected with and is vertically moveable with a vertically moveable chamber opening covering. Ideally, the seating device could also be used for unseating boards in the chamber, and can be used with a device having multiple chambers or chamber openings. Further, it would be beneficial for the seating device to be used to retrofit existing environmentally controllable chambers.